The Islamic State claimed responsibility on Tuesday for the Easter Sunday bombings at churches and hotels in Sri Lanka that killed more than 300 people. The group’s Amaq news agency called the bombers “Islamic State fighters.”

• A government official said the bombings were retaliation for the killing of 50 people last month at mosques in New Zealand, but he did not offer any evidence for the claim. He said they were carried out by two Islamist extremist groups.

• Sri Lanka’s highest-ranking Roman Catholic official, the archbishop of Colombo, joined elected officials and others in chastising the government for a serious lapse in security before the suicide bombings. The government was alerted that terrorists planned to attack churches, but failed to take action against them or pass on the warning.

• The first funerals were held at a damaged church in western Sri Lanka, where as many as 100 people were killed. The coffins, many bearing the remains of children, were interred as the police raised the death toll to 321. [Read about some of the victims.]

Islamic State says it was behind the Sri Lanka bombings

More than two days after the Sri Lanka bombings, the Islamic State claimed responsibility for the coordinated attacks.

The group’s news agency, Amaq, released a bulletin on Tuesday stating that the attacks were carried out by “Islamic State fighters.” The statement, which was disseminated on the group’s chat rooms on the app Telegram, also said that the bombings targeted Christians as well as citizens of countries belonging to the coalition fighting the Islamic State, also known as ISIS.

The group’s wording did not make clear whether it had direct ties to the bombers, or if the attackers were heeding the Islamic State’s calls for Muslims to attack in their home countries. The group has repeatedly called for assaults on churches, particularly since the New Zealand mosque attacks.

Whatever the links, the claim suggests that the recapture of territory once held by ISIS in Syria and Iraq does not mean the group is no longer a threat.

Tiny coffins laid to rest in mass burial

The coffins came one by one, some heavy and others much lighter.

As bulldozers cleared more space in a vacant lot near St. Sebastian’s Church in Negombo, barefoot men dripping with sweat scooped dirt with shovels in punishing heat.

One family stood in the shade. They were there for the burial of an 11-year-old boy.

“I don’t even know what to say,” said Lasanthi Anusha, a woman who came for the burial of her son’s classmate. “There were even smaller ones.”

Tuesday was the beginning of the first mass burials of the victims of the suicide attacks in Sri Lanka, which killed more than 300 people on Sunday, including many children. Soldiers and an armored personnel carrier lined the roads as the burials took place.

Of the half-dozen sites simultaneously attacked on Sunday, the church in Negombo was the hardest hit. As many as 100 people were killed there.

On Tuesday, priests wearing crisp white robes trimmed with black sashes held funerals in a large tent just outside the church. The funerals were scheduled to go on all day. The neighborhood around the church had been turned into an enormous, fortified mourning ground, with hundreds of soldiers deployed in every direction and little white flags fluttering in the wind.

Attack was in ‘retaliation’ for Christchurch, official claims

An initial investigation into the attacks suggests the bombers were hoping to avenge the killings of 50 Muslims in a shooting spree at two mosques in Christchurch, New Zealand, in March, a Sri Lankan government official said Tuesday.

“The preliminary investigations have revealed that what happened in Sri Lanka was in retaliation for the attack against Muslims in Christchurch,” the official, Ruwan Wijewardene, told the Parliament.

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Mr. Wijewardene, a junior defense minister, did not say what led investigators to that conclusion, and it was not clear how his statement aligned with warnings months earlier that Islamist radicals posed a serious threat and were stockpiling explosives and other weapons.

Officials said on Monday that a little-known Sri Lankan extremist group, National Thowheeth Jama’ath, had carried out the bombings.

But on Tuesday, Mr. Wijewardene said that two local Islamist radical groups were involved: National Thowheeth Jama’ath and Jammiyathul Millathu Ibrahim.

Government officials have said they believe the bombers were local, but had help from abroad.

Carrying a coffin at St. Sebastian’s Church.Credit:Adam Dean for The New York Times

National day of mourning as death toll rises

A full day of national mourning was declared across the country on Tuesday, as flags were lowered and a moment of silence was observed.

At 8:30 a.m., the time the first of six attacks were carried out on Sunday, Sri Lankans of differing faiths and ethnic groups bowed their heads and remained silent for three minutes.

Government officials said the number of people confirmed killed in the attacks was 321, up from 290 on Monday.

As part of the mourning period, liquor stores were ordered closed. Radio and television stations have played somber music throughout the day.

The front pages of local newspapers were similarly solemn on Tuesday. One, The Daily Mirror, printed a stark, all-black cover that read, “In remembrance of all those who lost their lives on 21.04.2019.”

‘Why wasn’t there any action?’ asks archbishop

Cardinal Malcolm Ranjith, the archbishop of Colombo, condemned the government on Tuesday for failing to act on an intelligence report that warned of a potential attack on churches.

“News media reported that there was information pertaining to a possible attack,” Cardinal Ranjith said at a news conference. “If that’s the case, couldn’t we have prevented the situation? Why wasn’t there any action?”

A security services briefing written at least 10 days before the bombings warned that National Thowheeth Jama’ath was planning to attack churches.

President Maithripala-Sirisena

Government responds with a curfew, social media blackout and more

Sri Lankan officials took a series of extraordinary steps in an effort to keep control of their shaken country, aiming to prevent further extremist attacks and retaliatory violence.

President Maithripala Sirisena said the government had given additional powers to the police and security forces to detain and interrogate people, and a curfew was imposed on Monday for the second day in a row, from 8 p.m. until 4 a.m. Officials said on Tuesday that the number of people arrested in connection with the case had grown to 40, from 24 on Monday.